As the UK goes through yet another heatwave, many of us are searching for any way we can to cool our homes down.14:37, 11 Jul 2026It's an age-old question that seems to be cropping up more frequently this summer than in previous years: does leaving your doors and windows open during a heatwave make your house hotter or cooler? While many of us frantically fling open our windows and crank up our fans, it can often feel as though we're simply pushing warm air around rather than actually cooling our homes down.‌With parts of the UK experiencing temperatures of 32°C this weekend, now seems the perfect moment to put the debate to rest: is it better to keep your windows open or shut during a heatwave?‌Keen to get a straight answer, I consulted several specialists, and their guidance was unanimous: keep windows, doors, blinds, and curtains firmly closed during the hottest periods of the day. This method keeps your home sealed off and reduces solar heat gain, helping rooms stay cooler.‌The specialists also suggested only opening windows and doors in the early morning or late evening, when the outside temperature drops below that indoors, to properly ventilate your home, reports Wales Online.'You're fighting a losing battle'Tina Loveland, Senior Designer at Appeal Shading, the UK's leading supplier of smart powered blinds, bespoke conservatory blinds, insect screens and awnings, explains: "Once sunlight has passed through a window and converted to heat inside a room, you're fighting a losing battle. Blinds and shutters intercept that heat before it reaches your living space, which is proven to actually reduce heat build-up.‌"A quality fitted blind on a sun-facing window can cut solar heat gain by 40-70%. Light-coloured or reflective fabrics work best - they bounce the energy back through the glass rather than absorbing it into the room. Dark blinds, by contrast, absorb heat and can actually make things worse."Conservatories deserve a special mention too. Without roof blinds, they can hit 40°C or above during a heatwave, radiating heat downwards into the house. If you have conservatory blinds, you need to make sure you keep these closed."Why shouldn't I open windows in a heatwave?Throwing open the windows during a heatwave feels like the obvious solution. Yet, according to Tina, this is actually the wrong approach.‌She explains: "It seems counterintuitive at first, but there's a really simple rule you can follow that puts it into perspective: if it's hotter outside than inside, opening your windows will warm your home up, not cool it down. During a UK heatwave, outdoor temperatures can stay above 30°C from mid-morning until early evening. If your home is sitting at 24°C or 25°C, cracking a window will actually just let hotter air in."NHS and Public Health England guidance echoes this advice: keep windows in rooms that are in direct sunlight closed during the hottest part of the day. The aim is to treat your home like a cool box - sealed and shaded until outdoor temperatures eventually begin to fall.‌When should I open windows in a heatwave?Tina said: "Once outdoor temperatures fall below what's inside - usually from around 9pm or 10pm in the peak of summer - that's when you should open your windows and blinds to let cooler air in and hotter air out. Open up fully, ideally on opposite sides of the house to create a cross-draught, and let the cooler air flush out the heat that's built up throughout the day."Max Wilson, co-founder of Pocket Storage, broadly concurs, recommending treating your home like a fridge between 10am and 6pm by keeping everything on the sunny side shut.‌"Opening your windows will either cool or warm up your house depending on how warm it is outside," he clarifies. "The major mistake most homeowners make is opening all their windows and doors for the entire day. The problem is, opening windows and doors when it is warmer outdoors is no different from opening a door to an oven."Why are UK houses so hot in heatwaves?"Houses in Britain are constructed in a way that conserves heat rather than repels it," said Max. "All of our insulating materials, furniture, carpets, bedding, even the walls of our homes, absorb heat all day long and then release that heat during the evening."‌Max also recommends moving clutter, furniture, laundry and storage boxes away from windows and doors to encourage air circulation. Congested hallways and blocked pathways can hinder airflow, leaving homes feeling stuffy and uncomfortably warm. His primary tip is to make sure there is an unobstructed path between opposite windows to maximise ventilation.He added: "Ultimately, it is not only about reducing the temperature of a house after it becomes very hot but rather preventing the temperature from rising in the first place. By closing windows when it is extremely hot and opening them when cooler air comes around and ensuring good circulation in the house, people can significantly cope during a heatwave."Use ice with fansJohn Klee, a heating technology expert at BestHeating, said: "There are various household tricks that can be used in addition to make hot weather more manageable. Many rely on fans in the UK to keep their rooms cool in the summer, but placing a bowl of ice in front of these can increase their effectiveness, circulating a cool breeze around a room rather than redistributing the same warm air."Article continues belowEdward Simon, director at Direct Fabrics, offered further advice: "Use internal doors deliberately. During the day, close off the hottest, sun-exposed rooms to stop heat drifting into cooler spaces. At night, open internal doors again so the whole house can clear stored heat. Finally, it's worth reducing indoor heat sources during peak hours, such as long oven cooking, tumble drying or running multiple heat-producing appliances, because those extra gains can tip a warm home into an uncomfortable one."